In a typical molding process, two halves of a mold are closed together to define a cavity and material is injected into the cavity to form a product. During the molding process, the two halves are repeatedly opened and closed to form multiple products. Molding processes are used in many industries. In many of these industries, the products being formed must meet rigorous standards and specifications. Hence, the tolerance for misalignment between the mold halves during the molding process is generally small.
Positioning devices are used to reduce tolerances between the mold halves to form products that meet the appropriate standards and specifications for each industry. A typical positioning device comprises a first member attached to one of the mold halves and a second member attached to the other mold half. The first member has a male portion that engages a female portion of the second member when the mold halves are closed together. An example of such a positioning device is shown in U.S. Pat. No. 5,762,977 to Boskovic.
The fit between the male and female portions of the members determines the magnitude of misalignment between the mold halves. In prior art positioning devices, the male portion includes a first pair of bearing surfaces and the female portion includes a second pair of bearing surfaces. The bearing surfaces of the male portion slide against the bearing surfaces of the female portion to provide a better fit when aligning and guiding the mold halves together. As a result, these bearing surfaces are susceptible to wear. Consequently, as demand for higher productivity increases, the speed of the molding process increases thereby increasing the wear along the bearing surfaces of prior art positioning devices.
Traditionally, when the bearing surfaces became worn, the positioning devices would be replaced. This resulted in increased cost and unacceptable delays in production. To solve this problem, the prior art has introduced the use of replaceable inserts in the positioning devices. This improvement is illustrated in U.S. Pat. No. 6,558,145 to Wieder. Wieder discloses a positioning device for a mold having a pair of separable mold halves. The positioning device includes a base mounted to one mold half and a head extending from the base. A receptacle is mounted to the other mold half and a pocket is defined in the receptacle for receiving the head. The head defines a plurality of channels with needle bearings disposed therein. The needle bearings bear against a sidewall of the pocket when the head is inserted into the pocket thereby reducing friction in the mating engagement of the head and pocket. The needle bearings are replaceable to reduce down time and increase productivity.